The present invention relates to a thrust reverser for a turbofan-type turbojet engine, more specifically such a thrust reverser incorporating a moveable deflector panel to minimize airstream turbulence in the fan duct.
In a turbofan-type turbojet engine, a cold flow air duct is located concentrically about a primary, hot-gas flow duct such that the upstream end of the cold flow air duct communicates with a fan driven by the turbojet engine. In instances where the bypass ratio is sufficiently high, a thrust reversing device may act on only the cold flow air and be incorporated into the housing defining the outer limits of the cold flow air duct in order to redirect the air passing through the duct into a thrust reversing position.
A typical thrust reversing device is shown in FIGS. 1, 2a and 2b. A housing 1 defines the outer limits of the cold flow air duct through which air flows in the direction of arrow 15 when the system is in the forward thrust mode. Housing 1 has an exterior surface panel 4, an interior surface panel 5 and a stationary frame structure 6 joining the downstream ends of the panels 4 and 5. A rear collar 3 extends downstream of a laterally facing opening, which may be covered by thrust reverser 2. The thrust reverser 2 comprises a plurality of thrust reversing doors 7 pivotally attached to the housing and connected to an actuator 7a. Actuator 7a is pivotally attached to stationary frame 6 and generally comprises a cylinder having an extendible and contractible piston rod connected to the door 7. Thrust reverser door 7 comprises an outer surface panel 9 and an inner surface panel 11 joined at their forwardmost ends by a reverse thrust deflector 13.
The door 7 is shown in the closed, forward thrust position in FIG. 1 wherein the laterally facing opening in the housing is closed and the air in the cold flow air duct passes in the direction of arrow 15. The outer surface panel 9 is substantially flush with the exterior surface panel 4 and the rear cone 3 to provide a smooth external air flow in the direction of arrow 10. FIG. 2a shows the turbofan type turbojet engine with the thrust reverser doors 7 in their closed positions.
When the doors 7 are displaced to their open, thrust reversing positions, the left side (as viewed in FIG. 1) is displaced upwardly (outwardly of the exterior surface 14) while the downstream end of the door 7 is displaced into the cold flow air duct. This position is illustrated in FIG. 2b wherein it can be seen that the laterally extending opening of the housing is opened and the downstream portion of the thrust reversing door 7 blocks off the cold flow air duct so as to redirect the air outwardly through the lateral opening to provide a thrust reversing force to the engine structure.
As best seen in FIG. 1, the inner surface panel 11 slopes toward the outer surface panel 9 in the upstream direction (toward the left as seen in FIG. 1). This enables reverse thrust deflector 13 to extend beyond the surface of the inner surface panel 11 to provide a more efficient air flow when the door is in the thrust reversing position. However, when door 7 is in the forward thrust position, a cavity 16 is created bounded by the inner surface panel 11, edge deflector 8 (fixedly attached to interior surface panel 5) and line 14, which is the theoretical smooth air flow line interconnecting the interior surface panel 5 with the downstream portion of door 7 and the rear collar 3. When the doors are in their closed, forward thrust positions, this cavity causes disturbances in the air flow passing through the cold flow air duct, thereby reducing the efficiency of the engine.
The air flow through the cold flow air duct can be made more efficient by moving the inner surface panel 11 closer toward the ideal air flow line 14, however, this reduces the length of the reverse thrust deflector 13 extending beyond the surface of inner surface panel 11 and reduces the efficiency of the system in the thrust reversing mode.
Attempts have been made to avoid these problems, as illustrated by U.S. Pat. Nos. 4,410,152 and 4,485,970 as well as French Pat. Nos. 2,559,838 and 2,618,853. While the structures set forth in these documents have improved the operational efficiency of the thrust reversers, they require a complex mechanism which increases complexity of the thrust reverser system and inherently reduces its reliability.